1. Field of Invention
The present invention relates to electronic devices, electro-optical devices, and electronic units having a current-driven device driven by electric current.
2. Description of Related Art
Currently, displays using liquid crystal have become quite popular as thin display apparatuses. This type of displays require lower power consumption and smaller spaces than CRT displays. Therefore, with the use of such display advantages, it is important to manufacture displays requiring lower power consumption and smaller spaces.
Some of the current displays use current-driven light-emitting devices instead of liquid crystal for display. Since the current-driven light-emitting devices emit light by themselves when current flows, unlike liquid crystal, the devices do not need backlight and can satisfy a market demand of low power consumption. In addition, the devices show superior display performances, such as a wide viewing angle and a high contrast. Among such current-driven light-emitting devices, electroluminescent devices are especially suited for displays because they can have a large area, a high definition, and full color. Further, among the electroluminescent devices, organic electroluminescent devices attract attentions because of their high quantum efficiency.
As such a display apparatus which uses an organic electroluminescent device, a display apparatus shown in FIG. 21 has been proposed. More specifically, in the display apparatus, pixel circuits are disposed correspondingly to the intersections of data lines X and scanning lines Y, the data lines are driven by a data driver 51, and the scanning lines Y are driven by the scanning driver 52.
The pixel circuit 55 is formed, for example, of two transistors 61 and 62, a capacitive device 63 for data storage, and an organic electroluminescent device 64, as shown in FIG. 22. A scanning line Y causes the transistor 61 to switch such that the capacitive device 63 holds a data signal sent from a data line X, as an electric charge. The electric charge held by the capacitive device 63 turns on the transistor 62, so that the amount of current corresponding to the data signal is supplied to the organic electroluminescent device 64. The organic electroluminescent device 64 emits light.
Current-driven devices, such as organic electroluminescent devices are more easily controlled by current than by a voltage. This results since the amount of current determines luminance in the organic electroluminescent devices, and therefore more accurate control is performed when current is used as a data signal.